Locking system

ABSTRACT

A movable member is retained in a predetermined position by means of a latch which is engageable with a catch on said member. The drive shaft of a pressure cylinder is connected to the latch and moves it to a retracted position when driven in one direction, thus permitting movement of the aforesaid member away from said predetermined position thereof. A latch retainer is arranged to retain the latch in its retracted position until the movable member contacts an arm of the latch retainer as the member returns to said predetermined position.

United States Patent [72] Inventor Robert L. Gudde Santee, Calif. [21 Appl. No. 809,279 [22] Filed Mar. 21,1969 [45] Patented Apr. 27, 1971 [73] Assignee Rohr Corporation Chula Vista, Calif.

[54] LOCKING SYSTEM l0Claims,4DrawingFigs.

521 U.S.Cl 292/201, 292/196 511 mu. E03c3/06 so FieldofSearch 292/12906l- [56] References Cited UNITED STATES PATENTS 2,538,980 1/1951 Payne 292/ 1 96X 2,896,990 7/1959 Garvey et a1..... 292/201X 3,090,644 5/1963 Fiala et al. 292/201X Primary Examiner-Emest R. Purser Att0rney-Ge0rge E. Pearson ABSTRACT: A movable member is retained in a predetermined position by means of a latch which is engageable with a catch on said member. The drive shaft of a pressure cylinder iscennected to the latch and moves it to a retracted position when driven in one direction, thus pennitting movement of the aforesaid member away from said predetermined position thereof. A latch retainer is arranged to retain the latch in its retracted position until the movable member contacts an arm of the latch retainer as the member returns to said predeten'nined position.

PM FHTF n APR 2 7 I971 SHEET 1 or 4 INVENTOR. ROBERT L. GUDDE ATTORNEY I J v u c 1 ATTORNEY PATENTEU APRZ? I971 SHEET UF 4 ATTORNEY LOCKING SYSTEM BACKGROUND OF THE INVENTION This invention relates to a system for retaining a movable member in a predetermined position when said member moves thereto and for releasing said member from said position by actuation of the system from a remote point at any selected time. More particularly, the invention relates to such a system which can advantageously be employed in jet aircraft.

Commercial jet-propelled aircraft generally are provided with thrust reversers comprising a plurality of so'called blocker doors which can be positioned to deflect thrust gas from jet engines in a direction opposite that which it normally takes to thereby decelerate the aircraft. It is obviously important to provide positive means for locking the aforesaid blocker doors in their inoperative, or retracted, position and for releasing them therefrom. It is also important for pilots of aircraft equipped with blocker doors to know that the latter have been properly retracted when deceleration is no longer blocker door has in fact been placed in such condition.

SUMMARY OF THE INVENTION In accordance with this invention, a movable member is retained in a fixed position by means of a hook-shaped latch one end of which is pivoted to a stationary support disposed adjacent the member when it is in its fixed position (in the case of the preferred embodiment of the invention described hereinafter, the stationary support is mounted on the nacelle of a jet-propelled airplane and the movable member is a blocker door). When the latch is in an operative (or locking) position, the throat thereof extends partially around a cylindrical catch fixedly secured to the movable member. The latch is resiliently biased toward its locking position by means of a spring but can be rotated to an inoperative (or retracted) position, wherein the latch is spaced from the catch, by means of an actuator carried by the support and comprising an extensible drive member one end of which is connected to the latch. The connection between the latch and the drive member is such that the latter can return to its initial position after it has retracted the latch, without thereby moving the latch from the retracted position thereof. In its retracted position the latch is disposed adjacent a stop fixedly mounted on the support, and a latch retainer is mounted on the support for rotation between a first position spaced from this stop and a second position in contact therewith. The latch retainer comprises a first arm engageable with the latch when the latch retainer is in said second position thereof to thereby prevent the latch from returning to its locking position. The latch retainer also comprises a second arm which extends laterally from the first arm and which is disposed in the path of movement of the movable member when the latch retainer is in said second position thereof. The latch retainer is resiliently biased toward the second position thereof by means of a spring that is stronger than the aforementioned spring that biases the latch. Thus when the drive member returns to its initial position, the latch retainer holds the latch in its retracted position. However, as the movable member moves toward the position where it can be fixedly secured by the latch, the member contacts the second arm of the latch retainer and rotates the latch retainer to the first position thereof, thereby allowing the latch to return to its locking position. In the preferred embodiment of the invention, the catch on the movable member engages a cam surface on the latch as the member moves toward the position where it will be secured, and the latch is temporarily displaced from its locking position.

OBJECTS OF THE INVENTION Accordingly, it is a broad object of this invention to provide effective means for retaining a member at a predetermined position when the member moves into said position, and for releasing the member from said position at any selected time.

Another object of the invention is to provide a locking and releasing system adapted to be actuated from a remote point.

An additional object is to provide a reliable locking and releasing system.

Still another object is to provide a locking and releasing system the operational condition of which is always correctly reported to a remote point.

A further object is to provide an improved system for locking a blocker door of a jet-propelled airplane in retracted position relative to an engine nacelle and for releasing said blocker door from the retractedposition.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an end elevation of components of a preferred embodiment of the present invention which are mounted on a support attached to the tailpipe of a jet engine and to the nacelle enclosing the engine, components which are associated with a deployable blocker door not being shown in the drawing;

FIG. 2 is a partially sectional side elevation of components of the preferred embodiment, the drawing illustrating those components which are mounted on the blocker door which is not shown in FIG. 1;

FIG. 3 is a partially sectional side elevation of the components illustrated in FIG. 2, the drawing showing the retracted position of the latch which locks the aforesaid blocker door in a stowed position on the nacelle;

FIG. 4 is a side elevation of the same components, some of which are illustrated in positions different from those of the same components illustrated in FIGS. 2 and 3.

Throughout the drawings and the following specification, the same numbers indicate the same parts.

DETAILED DESCRIPTION The preferred embodiment of the invention is employed to lock a blocker door in a stowed position relative to the engine nacelle of a jet-propelled aircraft and, at a selected time, to release the blocker door so that it can be extended to a position wherein it deflects exhaust gas laterally of said nacelle to provide thrust reversal. In FIG. l the numbers 10 and 11 respectively generally desigiate the tailpipe of a jet engine and a nacelle enclosing said tailpipe. FIG. 2 illustrates in cross section the forward end of a blocker door, generally designated by the number 12, which comprises an outer wall 13 and a forward wall formed of three sheet metal stampings MA, MB, MC which are fixedly joined together by suitable means such as welding. A bracket 16 is fixedly attached to the forward surface of member MA and comprises two parallel arms which project perpendicularly therefrom, and a cylindrical catch 18 is fixedly mounted between the arms of this bracket so that its longitudinal axis is parallel with the inwardly projecting portion of said member 14 and disposed lengthwise thereof.

Generally designated in the drawings by the number 20 is a support formed of sheet metal stampings which are fixedly joined together by suitable means such as welding. More explicitly, support 20 comprises a centrally apertured member 22 which is bolted to a structural member 24 which is in turn welded to the inner surface of the outer wall 25 of nacelle 11, two parallel channels 26, 28 (see FIG. 1) which project from the forward side of said member 22, and two parallel brackets 30,32 which project from the aft side of the same member. Rib 24 comprises a plurality of sheet metal stampings which are welded together, and a ring 33 is fastened to the outwardly facing surface on one of these stampings. Member 22 is also bolted to a structural member 35 which is suitably secured to the outer surface of tailpipe 10. Each bracket 30, 32 has a hole formed in the end portion thereof, and the shank of a bolt, hereinafter referred to as pin 34, extends through these holes and is retained therein by means of a nut 36. An elongate stop 38 is fixedly mounted on member 22 of support 20 between brackets 30, 32 and projects from the aft side thereof at a point adjacent pin 34. The number 40 generally designates a hook-shaped latch which is pivoted to pin 34 and the throat 42 of which extends partially around catch 18 when blocker door and the latch are positioned as illustrated in FIG. 2. More explicitly, latch 40 comprises an apertured hub 44 through which pin 34 extends, a shank portion 46 disposed perpendicular to the longitudinal axis of pin 34, and a head portion 48 which is also disposed perpendicular to said longitudinal axis and which extends laterally from shank portion 46. Extending between the sides of the head portion of latch 40 is an elongate slot 50 the longitudinal axis of which is disposed lateral to the shank portion of the latch. Latch 40 is also provided with a cylindrical contact member 52 that projects laterally from one side of said shank portion thereof, a lug 54 that projects from the other side of said shank portion, and an elongate indicator am 55 which extends laterally from the rear edge of the head portion thereof.

Disposed adjacent one side of latch 40 is a latch retainer which is generally designated by the number 56 and which comprises an apertured hub 58 through which pin 34 extends, a first arm 60 extending perpendicularly from said hub, and a second arm 62 also extending perpendicularly from said hub on the side thereof remote from stop 38. Second arm 62 is obliquely disposed with respect to first arm 60 and, as illustrated in FIGS. 2 and 4, is engageable by member 14C of blocker door 12. As will be described in detail hereinafter, latch 40 and latch retainer 56 are both rotatable between first and second positions thereof.

As can best be seen in FIG. 1, a torsion spring 64 is coiled around hub 44 of latch 40, opposite ends of said spring projecting laterally from said hub and respectively engaging lug 54 and stop 38. More particularly, the ends of spring 64 are forced toward each other when the spring is placed in the illustrated position, and thus the end of the spring which contacts stop 38 remains in fixed position relative to support while the other end of the spring tends to move clockwise of pin 34 (in the view of the latter shown in FIG. 2) and to rotate latch 40 in the same direction. Latch retainer 56 is biased to rotate in the opposite direction by means of a helical spring 66 one end of which is engaged with the edge of a hole formed in member 26 of support 20 and the other end of which is engaged with first arm 60 of said latch retainer. For a reason which will be disclosed hereinafter, spring 66 must be stronger than spring 64. Preferably spring 66 has a rating of about 65-75 inch-pounds and spring 64 has a rating of about l923 inch-pounds.

Support 20 also comprises a bracket which is fixedly attached to members 26, 28 and formed with two parallel arms 68 (only one of which is illustrated, in FIG. 2). A pin 70 extends through holes in the aforesaid brackets and through a hole in a lug 72 formed on one end of a pressure cylinder 74, the longitudinal axis of said pin being parallel with the longitudinal axis of pin 34. A drive member 76 is slidably disposed within a hole in the end cap 78 on the free end of cylinder 74, and the inner end of this drive member is connected to a piston 80 slidably disposed within said cylinder. Movement of piston 80 toward end cap 78 is limited by means of a stop pin 82 which extends through a hole in the wall of cylinder 74. A pair of pressure fluid conduits 84, 86 are respectively connected to opposite ends of cylinder 74 and communicate with the interior thereof. These conduits are connected to conventional means (not shown) for providing a differential pressure to opposite sides of piston 80 to thereby drive the piston in opposite directions within cylinder 74. A clevis 88 is threadedly engaged with the free end of drive member 76 and is held in fixed position relative thereto by means of a locknut 90. An annular roller 92 (see FIG. 1) is transversely disposed within the slot 50 in latch 40 and engaged with the longitudinally extending walls thereof, and the shaft of a machine screw 94 extends through this roller and through holes in the ends of clevis 88. A washer 96 is disposed between the head of screw 94 and the adjacent am of clevis 88, and another washer 98 is disposed between the other arm of the clevis and a nut 100 engaged with the end of the screw. Nut 100 is retained in fixed position relative to the shaft of screw 94 by means ofa cotter pin (not shown).

Fixedly mounted on a support member 101 which extends between and is fixedly joined to channels 26, 28 of support 20 is a magnetic-type proximity sensor 102, preferably of the type sold by Electro Development Corporation, Lynwood, Wash. When indicator arm moves from the position thereof illustrated in FIGS. 3 and 4 to the position thereof illustrated in FIG. 2, proximity sensor 102 transmits a signal to a control point which indicates that latch 40 has returned to a position where it can lock blocker door 12 in a stowed position on nacelles 11.

OPERATION Catch 18 travels along an arcuate path when blocker door 12 is extended to its operative position (which movement is effected by actuators, not shown, carried by nacelle l1 and connected to the blocker door). FIG. 2 illustrates latch 40 in a first position thereof wherein the latch is rotated away from stop 38. Drive member 76 is also illustrated in a first position thereof relative to cylinder 74 and support 20, namely, a position wherein the drive member is fully extended and piston is engaged with stop pin 82. More explicitly, when latch 40 and drive member 76 are both in the first positions thereof, roller 92 abuts the end surface of slot 50 which is nearest the longitudinal axis of the shank portion 46 of the latch. Thus drive member 76 prevents further rotation of latch 40 in a clockwise direction as viewed in FIG. 2. It should be noted that when blocker door 12 is in its illustrated fully retracted position and latch 40 in the first position thereof, the throat 42 of the latch extends partially around catch 18 but does not contact the periphery thereof. However, under certain flight conditions of the aircraft with which blocker door 12 is associated, the blocker door is urged away from its fully retracted position by aerodynamic forces applied thereto, and thus catch 18 moves into contact with latch 40 and the latter thereby prevents blocker door from being extended when it should not be. The inner edge of member 14C of blocker door 12 contacts second arm 62 of latch retainer 56 when blocker door 12 is in the fully retracted position thereof which is illustrated in FIG. 2. Since latch retainer 56 is biased toward stop 38 by means of spring 66, as blocker door 12 moves away from the position illustrated in FIG. 2 (as a result of the aforesaid aerodynamic forces applied thereto under certain flight conditions) second arm 62 follows the movement of member 14C. Thus if first arm 60 of latch retainer 56 were in contact with contact member 52 of latch 40 when blocker door 12 is in its fully retracted position, the latch would be rotated toward stop 38 by said first arm as blocker door moves outwardly. This action would be undesirable because it would move latch 40 away from the position where it is designed to be located in order to block movement of catch 18 (and thus movement of blocker door 12). Hence latch retainer 56 is designed so that first arm 60 thereof is spaced a short distance from contact member 52 of latch 40 when blocker door 12 is in its fully retracted position, and catch 18 thus engages latch 40, and is restrained thereby, before said first arm engages said contact member.

When blocker door 12 is to be extended to its operative position, hydraulic fluid is forced into the end of cylinder 74 which is on the right in FIG. 2, thereby moving drive member 76 to a second position thereof shown in FIG. 3 and rotating latch 40 to the second position thereof which is illustrated the same drawing. When latch 40 is rotated toward stop 38 by the aforesaid action of cylinder 74, blocker door 12 may be causes latch retainer 56 to rotate with latch 40 until said latch retainer contacts stop 38. However, latch 40 is rotated a short distance beyond its position when latch retainer 56 contacts stop 38, this additional rotation of the latch being effected to provide proper clearance for catch l8 as it moves past the tip of the hook of the latch. It should be pointed out that the signal transmitted by sensor 102 indicatesthat latch 40 has moved from its locking position when indicator arm 55 is moved away from the sensor to the positions thereof illustrated in FIGS. 3 and 4.

When blocker door 12 is to be retracted to its stowed position on nacelle 11 by actuation of the hydraulic cylinders associated therewith, cylinder 74 is simultaneously actuated to return drive member 76 to the first position thereof illustrated in FIG. 2. Since roller 92 and the shank of screw 94 are free to move longitudinally of slot 50, this movement of drive member 76 can be accomplished without simultaneously rotating latch 40 into the first thereof also illustrated in FIG. 2. However, as drive member 76 moves toward the first position thereof, latch 40 is pulled by spring 64 into a third position thereof which is illustrated in FIG. 4, namely, a position wherein contact member 52 of the latch abuts first arm 60 of latch retainer 56. Since spring 66 is stronger than spring 64, latch retainer 56 then retains latch 40 in said third position thereof until the inner edge of member 14C contacts second arm 62 of the latch retainer and rotates the latter to the position thereof which is illustrated in FIG. 2, thus allowing the latch to rotate to the first position thereof which is also illustrated in the last-mentioned drawing. Because of the difference in size of cylinder 74 and the hydraulic actuators which are associated with blocker door 12, drive member 76 is returned to the first position thereof before the blocker door reaches the position thereof which is illustrated in FIG. 4. As blocker door 12 is pulled by its actuators into the retracted position, catch 18 strikes a cam surface 104 on the head portion of latch 40 and the latch is displaced toward stop 38 until the catch slides off the tip of the book of said latch. As latch 40 is returned to its locking position, indicator arm 55 causes proximity sensor M2 to transmit a signal which indicates that latch 40 has returned to its locking position. Since latch 40 is held in the aforesaid third position thereof until blocker door 112 contacts second arm 62 of latch retainer 56 and allows the latch to return to its locking position,'it is impossible for the latch to return to said locking position while blocker door 12 is extended.

Although this invention has been described with reference to a particular embodiment of the same, it should not be considered to be limited thereto for various modifications could be made therein by one having ordinary skill in the art without departing from the spirit and scope of the invention as defined in the following claims.

What is claimed as new and useful and desired to be secured by Letters Patent is:

Iclaim:

l. A system for locking a movable member in a fixed position and releasing it therefrom, comprising:

a catch fixedly mounted on said movable member;

a. stationary support disposed adjacent said movable member when the latter is in said fixed position thereof;

a pin fixedly mounted on said support;

a stop fixedly mounted on said support adjacent said pin;

a latch mounted on said pin for rotation between a first locking position remote from said stop and a second retracted position nearer said stop, said latch being disposed substantially perpendicular to the longitudinal axis of said support pin and coacting with said catch to prevent movement of said movable member away from said fixed position thereof when said latch is in said first position thereof;

first biasing means carried by said support and adapted to resiliently bias said latch toward said first position thereof; latch retainer mounted on said support for rotation between a first position spaced from said stop and a second position in contact therewith, said latch retainer comprising a first arm engageable with said latch when said latch retainer is in said second position thereof to thereby prevent said latch from returning to said first position thereof and a second arm extending laterally from said first arm on the side thereof remote from said stop and engageable by said movable member; second biasing means carried by said support and adapted to resiliently bias said latch retainer toward said second position thereof, said second biasing means being stronger than first biasing means; and actuating means comprising a drive motor mounted on said support and a drive member operatively' associated with said drive motor and movable thereby between first and second positions relative to said support, said drive member and said latch being arranged so that said drive member engages said latch when moved from said first to 7 said second position thereof and thereby rotates said latch from said first to said second position thereof, and so that said drive member can thereafter return to said first position thereof without moving said latch from said second position thereof, said latch retainer and said second biasing means coacting to retain said latch in said second position thereof until said movable member contacts said second arm while moving to said fixed position thereof and thereby rotates said latch retainer to said first position thereof.

2. The system defined in claim 1 wherein said latch and said latch retainer are both mounted on said pin.

3. The system defined in claim 1 wherein said first biasing means comprises a torsion spring and said second biasing means comprising a helical spring.

4. The system defined in claim 1 wherein said actuating means comprising a pressure cylinder and drive shaft associated therewith.

5. The system defined in claim I wherein said catch is arranged to strike said latch as said movable member moves to said fixed position thereof, whereby said latch is temporarily displaced from said first position thereof.

6. A system for locking a movable member in a fixed position and releasing it therefrom, comprising:

a catch fixedly mounted on said movable member;

a stationary support disposed adjacent said movable member when the latter is in said fixed position thereof;

a pin fixedly mounted on said support;

a stop fixedly mounted on said support adjacent said pin;

a latch mounted on said pin for rotation between a first locking position remote from said stop and a second retracted position nearer said stop, said latch being disposed substantially perpendicular to the longitudinal axis of said pin and coacting with said catch to prevent movement of said movable member away from said fixed position thereof when said latch is in said first position thereof, said latch comprising a shank portion and an integral head portion extending laterally from said shank portion, said head portion having formed therein a slot which extends between the sides thereof and the longitudinal axis of which is disposed lateral to said shank portion, said latch also comprising a contact member which projects from one side of said shank portion thereof;

a torsion spring disposed around said pin and opposite ends of which project laterally therefrom, one end of said torsion spring being fixedly positioned relative to said support and the other end thereof engaging said latch to thereby resiliently bias the latter toward said first position thereof;

a latch retainer mounted on said pin for rotation between a first position spaced from said stop and a second position in contact therewith, said latch retainer comprising a first arm engageable with said contact member when said latch retainer is in said second position thereof to thereby prevent said latch from returning to said first position thereof and a second arm extending laterally from said first arm on the side thereof remote from said stop and engageable by said movable member;

a helical spring one end of which is connected to said support and the other end of which is connected to said first arm to thereby resiliently bias said latch retainer toward said second position thereof, said helical spring being stronger than said torsion spring;

a slide member slidably disposed within said slot and at least one end of which projects laterally therefrom;

and a pressure cylinder and a drive member operatively associated therewith, said pressure cylinder being mounted on said support for rotation about an axis disposed substantially parallel with the longitudinal axis of said pin and the free end of said drive member being connected to said slide member, retraction of said drive member relative to said pressure cylinder rotating said latch from said first to said second position thereof, said latch retainer and said helical spring coacting to retain said latch in said second position thereof until said movable member contacts said second arm while moving to said fixed position thereof and thereby rotates said latch retainer to said first position thereof.

7. ln combination with a blocker door mounted on a jetengine nacelle for movement between retracted and extended positions, a locking and releasing system comprising:

supporting means fixedly mounted on said blocker door adjacent the forward edge thereof and projecting laterally from the inner side thereof;

a catch fixedly mounted on said supporting means;

a support fixedly mounted on said nacelle;

a pin fixedly mounted on said support;

a stop fixedly mounted on said support adjacent said pin;

a latch mounted on said pin for rotation between a first locking position remote from said stop and a second retracted position nearer said stop, said latch coacting with said catch to prevent movement of said blocker door away from said retracted position thereof when said latch is in said first position thereof, said latch comprising an apertured hub through which said pin extends, a shank portion extending laterally from said hub, and an integral head portion extending laterally from said shank portion, said head portion having formed therein a slot which extends between the sides thereof and the longitudinal axis of which is disposed lateral to said shank portion, said latch also comprising a contact member which projects from one side of said shank portion thereof;

a latch retainer mounted on said pin for rotation between a first position spaced from said stop and a second position in contact therewith, said latch retainer comprising an apertured hub through which said pin extends, a first arm extending laterally from said hub and engageable with said contact member when said latch retainer is in said second position thereof to thereby prevent said latch from returning to said second position thereof, and a second arm extending laterally from said hub and said first arm on the side of the latter remote from said stop and engageable by said supporting means;

a torsion spring disposed around the hub of said latch and opposite ends of which project laterally therefrom, one end of said torsion spring being fixedly positioned relatively to said support and the other end thereof engaging said latch to thereby resiliently bias the latter toward said first position thereof;

a helical spring one end of which is connected to said support and the other end of which is connected to said first arm to thereby resilientl bias said latch retainer toward said second position t ereof, said helical spring being stronger than said torsion spring; and

an annular roller slidably disposed within said slot in said latch and a shaft extending through said roller and projecting from opposite ends thereof, the longitudinal axis of said shaft being disposed substantially parallel with the longitudinal axis of said pin;

a pressure cylinder, a drive member operatively associated therewith, and a clevis mounted on the free end of said drive member, said pressure cylinder being mounted on said support for rotation about an axis disposed substantially parallel with the longitudinal axis of said pin and the ends of said clevis being respectively connected to the ends of said shaft, retraction of said drive member relative to said pressure cylinder rotating said latch from said first to said second position thereof, said latch retainer and said helical spring coacting to retain said latch in said second position thereof until said supporting means contacts said second arm when said blocker door moves to the retracted position thereof and thereby rotates said latch retainer to said first position thereof.

8. The system defined in claim 7 including sensing means carried by said nacelle and adapted to transmit to a point remote from said nacelle a signal representative of the position of said latch.

9. The system defined in claim 8 wherein said sensing means comprises:

an indicator arm projecting from one side of said latch; and

an electrical sensor fixedly positioned on said support so that said indicator arm is adjacent thereto when said latch is in said first position thereof and spaced therefrom when said latch is in said second position thereof, said sensor being adapted to transmit to said remote point an electrical signal the intensity of which depends upon the position of said indicator arm relative thereto.

10. The system defined in claim 8 wherein said first arm is spaced from said contact member when said blocker door is in the retracted position thereof. 

1. A system for locking a movable member in a fixed position and releasing it therefrom, comprising: a catch fixedly mounted on said movable member; a stationary support disposed adjacent said movable member when the latter is in said fixed position thereof; a pin fixedly mounted on said support; a stop fixedly mounted on said support adjacent said pin; a latch mounted on said pin for rotation between a first locking position remote from said stop and a second retracted position nearer said stop, said latch being disposed substantially perpendicular to the longitudinal axis of said support pin and coacting with said catch to prevent movement of said movable member away from said fixed position thereof when said latch is in said first position thereof; first biasing means carried by said support and adapted to resiliently bias said latch toward said first position thereof; a latch retainer mounted on said support for rotation between a first position spaced from said stop and a second position in contact therewith, said latch retainer comprising a first arm engageable with said latch when said latch retainer is in said second position thereof to thereby prevent said latch from returning to said first position thereof and a second arm extending laterally from said first arm on the side thereof remote from said stop and engageable by said movable member; second biasing means carried by said support and adapted to resiliently bias said latch retainer toward said second position thereof, said second biasing means being stronger than first biasing means; and actuating means comprising a drive motor mounted on said support and a drive member operatively associated with said drive motor and movable thereby between first and second positions relative to said support, said drive member and said latch being arranged so that said drive member engages said latch when moved from said first to said second position thereof and thereby rotates said latch from said first to said second position thereof, and so that said drive member can thereafter return to said first position thereof without moving said latch from said second position thereof, said latch retainer and said second biasing means coacting to retain said latch in said second position thereof until said movable member contacts said second arm while moving to said fixed position thereof and thereby rotates said latch retainer to said first position thereof.
 2. The system defined in claim 1 wherein said latch and said latch retainer are both mounted on said pin.
 3. The system defined in claim 1 wherein said first biasing means comprises a torsion spring and said second biasing means comprising a helical spring.
 4. The system defined in claim 1 wherein said actuating means comprising a pressure cylinder and drive shaft associated therewith.
 5. The system defined in claim 1 wherein said catch is arranged to strike said latch as said movable member moves to said fixed position thereof, whereby said latch is temporarily displaced from said first position thereof.
 6. A system for locking a movable member in a fixed position and releasing it therefrom, comprising: a catch fixedly mounted on said movable member; a stationary support disposed adjacent said moVable member when the latter is in said fixed position thereof; a pin fixedly mounted on said support; a stop fixedly mounted on said support adjacent said pin; a latch mounted on said pin for rotation between a first locking position remote from said stop and a second retracted position nearer said stop, said latch being disposed substantially perpendicular to the longitudinal axis of said pin and coacting with said catch to prevent movement of said movable member away from said fixed position thereof when said latch is in said first position thereof, said latch comprising a shank portion and an integral head portion extending laterally from said shank portion, said head portion having formed therein a slot which extends between the sides thereof and the longitudinal axis of which is disposed lateral to said shank portion, said latch also comprising a contact member which projects from one side of said shank portion thereof; a torsion spring disposed around said pin and opposite ends of which project laterally therefrom, one end of said torsion spring being fixedly positioned relative to said support and the other end thereof engaging said latch to thereby resiliently bias the latter toward said first position thereof; a latch retainer mounted on said pin for rotation between a first position spaced from said stop and a second position in contact therewith, said latch retainer comprising a first arm engageable with said contact member when said latch retainer is in said second position thereof to thereby prevent said latch from returning to said first position thereof and a second arm extending laterally from said first arm on the side thereof remote from said stop and engageable by said movable member; a helical spring one end of which is connected to said support and the other end of which is connected to said first arm to thereby resiliently bias said latch retainer toward said second position thereof, said helical spring being stronger than said torsion spring; a slide member slidably disposed within said slot and at least one end of which projects laterally therefrom; and a pressure cylinder and a drive member operatively associated therewith, said pressure cylinder being mounted on said support for rotation about an axis disposed substantially parallel with the longitudinal axis of said pin and the free end of said drive member being connected to said slide member, retraction of said drive member relative to said pressure cylinder rotating said latch from said first to said second position thereof, said latch retainer and said helical spring coacting to retain said latch in said second position thereof until said movable member contacts said second arm while moving to said fixed position thereof and thereby rotates said latch retainer to said first position thereof.
 7. In combination with a blocker door mounted on a jet-engine nacelle for movement between retracted and extended positions, a locking and releasing system comprising: supporting means fixedly mounted on said blocker door adjacent the forward edge thereof and projecting laterally from the inner side thereof; a catch fixedly mounted on said supporting means; a support fixedly mounted on said nacelle; a pin fixedly mounted on said support; a stop fixedly mounted on said support adjacent said pin; a latch mounted on said pin for rotation between a first locking position remote from said stop and a second retracted position nearer said stop, said latch coacting with said catch to prevent movement of said blocker door away from said retracted position thereof when said latch is in said first position thereof, said latch comprising an apertured hub through which said pin extends, a shank portion extending laterally from said hub, and an integral head portion extending laterally from said shank portion, said head portion having formed therein a slot which extends between the sides thereof and the longitudinal axis of which is disposed lateral to saId shank portion, said latch also comprising a contact member which projects from one side of said shank portion thereof; a latch retainer mounted on said pin for rotation between a first position spaced from said stop and a second position in contact therewith, said latch retainer comprising an apertured hub through which said pin extends, a first arm extending laterally from said hub and engageable with said contact member when said latch retainer is in said second position thereof to thereby prevent said latch from returning to said second position thereof, and a second arm extending laterally from said hub and said first arm on the side of the latter remote from said stop and engageable by said supporting means; a torsion spring disposed around the hub of said latch and opposite ends of which project laterally therefrom, one end of said torsion spring being fixedly positioned relatively to said support and the other end thereof engaging said latch to thereby resiliently bias the latter toward said first position thereof; a helical spring one end of which is connected to said support and the other end of which is connected to said first arm to thereby resiliently bias said latch retainer toward said second position thereof, said helical spring being stronger than said torsion spring; and an annular roller slidably disposed within said slot in said latch and a shaft extending through said roller and projecting from opposite ends thereof, the longitudinal axis of said shaft being disposed substantially parallel with the longitudinal axis of said pin; a pressure cylinder, a drive member operatively associated therewith, and a clevis mounted on the free end of said drive member, said pressure cylinder being mounted on said support for rotation about an axis disposed substantially parallel with the longitudinal axis of said pin and the ends of said clevis being respectively connected to the ends of said shaft, retraction of said drive member relative to said pressure cylinder rotating said latch from said first to said second position thereof, said latch retainer and said helical spring coacting to retain said latch in said second position thereof until said supporting means contacts said second arm when said blocker door moves to the retracted position thereof and thereby rotates said latch retainer to said first position thereof.
 8. The system defined in claim 7 including sensing means carried by said nacelle and adapted to transmit to a point remote from said nacelle a signal representative of the position of said latch.
 9. The system defined in claim 8 wherein said sensing means comprises: an indicator arm projecting from one side of said latch; and an electrical sensor fixedly positioned on said support so that said indicator arm is adjacent thereto when said latch is in said first position thereof and spaced therefrom when said latch is in said second position thereof, said sensor being adapted to transmit to said remote point an electrical signal the intensity of which depends upon the position of said indicator arm relative thereto.
 10. The system defined in claim 8 wherein said first arm is spaced from said contact member when said blocker door is in the retracted position thereof. 